High performance Broadband Photodetection Based on Graphene -- MoS$_{2x}$Se$_{2(1-x)}$ Alloy Engineered Phototransistors

The concept of alloy engineering has emerged as a viable technique towards tuning the bandgap as well as engineering the defect levels in two-dimensional transition metal dichalcognides (TMDC). Possibility to synthesize these ultrathin TMDC materials through chemical route has opened realistic possibilities to fabricate hybrid multi-functional devices. By synthesizing nanosheets with different composites of MoS$_{2x}$Se$_{2(1-x)}$ (x = 0 to 1) using simple chemical methods, we systematically investigate the photo response properties of three terminal hybrid devices by decorating large area graphene with these nanosheets (x = 0, 0.5, 1) in 2D-2D configurations. Among them, graphene-MoSSe hybrid phototransistor exhibits superior optoelectronic properties than its binary counterparts. The device exhibits extremely high photoresponsivity (>10$^4$ A/W), low noise equivalent power (~10$^{-14}$ W/Hz$^{0.5}$), higher specific detectivity (~ 10$^{11}$ Jones) in the wide UV-NIR (365-810 nm) range with excellent gate tunability. The broadband light absorption of MoSSe, ultrafast charge transport in graphene, along with controllable defect engineering in MoSSe makes this device extremely attractive. Our work demonstrates the large area scalability with wafer-scale production of MoS$_{2x}$Se$_{2(1-x)}$ alloys, having important implication towards facile and scalable fabrication of high-performance optoelectronic devices and providing important insights into the fundamental interactions between van-der-Waals materials.